/* Copyright (c) 2020 XEPIC Corporation Limited */
/*
 * Copyright (c) 2012-2013 Stephen Williams (steve@icarus.com)
 *
 *    This source code is free software; you can redistribute it
 *    and/or modify it in source code form under the terms of the GNU
 *    General Public License as published by the Free Software
 *    Foundation; either version 2 of the License, or (at your option)
 *    any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA.
 */

#include <assert.h>
#include <string.h>

#include "vvp_priv.h"

static void fallback_eval(ivl_expr_t expr) {
  draw_eval_vec4(expr);
  fprintf(vvp_out, "    %%pushv/str; Cast BOOL/LOGIC to string\n");
}

static void string_ex_concat(ivl_expr_t expr) {
  unsigned repeat;

  assert(ivl_expr_parms(expr) != 0);
  assert(ivl_expr_repeat(expr) != 0);

  /* Push the first string onto the stack, no matter what. */
  draw_eval_string(ivl_expr_parm(expr, 0));

  for (repeat = 0; repeat < ivl_expr_repeat(expr); repeat += 1) {
    unsigned idx;
    for (idx = (repeat == 0) ? 1 : 0; idx < ivl_expr_parms(expr); idx += 1) {
      ivl_expr_t sub = ivl_expr_parm(expr, idx);

      /* Special case: If operand is a string literal,
         then concat it using the %concati/str
         instruction. */
      if (ivl_expr_type(sub) == IVL_EX_STRING) {
        fprintf(vvp_out, "    %%concati/str \"%s\";\n", ivl_expr_string(sub));
        continue;
      }

      draw_eval_string(sub);
      fprintf(vvp_out, "    %%concat/str;\n");
    }
  }
}

static void string_ex_property(ivl_expr_t expr) {
  ivl_signal_t sig = ivl_expr_signal(expr);
  unsigned pidx = ivl_expr_property_idx(expr);

  fprintf(vvp_out, "    %%load/obj v%p_0;\n", sig);
  fprintf(vvp_out, "    %%prop/str %u;\n", pidx);
  fprintf(vvp_out, "    %%pop/obj 1, 0;\n");
}

static void string_ex_signal(ivl_expr_t expr) {
  ivl_signal_t sig = ivl_expr_signal(expr);

  if (ivl_signal_data_type(sig) != IVL_VT_STRING) {
    fallback_eval(expr);
    return;
  }

  /* Special Case: If the signal is the return value of the
     function, then use a different opcode to get the value. */
  if (signal_is_return_value(sig)) {
    assert(ivl_signal_dimensions(sig) == 0);
    fprintf(vvp_out, "    %%retload/str 0; Load %s (string_ex_signal)\n",
            ivl_signal_basename(sig));
    return;
  }

  /* Simple case: This is a simple variable. Generate a load
     statement to load the string into the stack. */
  if (ivl_signal_dimensions(sig) == 0) {
    fprintf(vvp_out, "    %%load/str v%p_0;\n", sig);
    return;
  }

  /* There is a word select expression, so load the index into a
     register and load from the array. */
  ivl_expr_t word_ex = ivl_expr_oper1(expr);
  int word_ix = allocate_word();
  draw_eval_expr_into_integer(word_ex, word_ix);
  fprintf(vvp_out, "    %%load/stra v%p, %d;\n", sig, word_ix);
  clr_word(word_ix);
}

static void string_ex_select(ivl_expr_t expr) {
  /* The sube references the expression to be selected from. */
  ivl_expr_t sube = ivl_expr_oper1(expr);
  /* This is the select expression */
  ivl_expr_t shift = ivl_expr_oper2(expr);

  /* Assume the sub-expression is a signal */
  ivl_signal_t sig = ivl_expr_signal(sube);
  assert(ivl_signal_data_type(sig) == IVL_VT_DARRAY ||
         ivl_signal_data_type(sig) == IVL_VT_QUEUE);

  draw_eval_expr_into_integer(shift, 3);
  fprintf(vvp_out, "    %%load/dar/str v%p_0;\n", sig);
}

static void string_ex_string(ivl_expr_t expr) {
  const char* val = ivl_expr_string(expr);

  /* Special case: The elaborator converts the string "" to an
     8-bit zero, which is in turn escaped to the 4-character
     string \000. Detect this special case and convert it back
     to an empty string. [Perhaps elaboration should be fixed?] */
  if (ivl_expr_width(expr) == 8 && (strcmp(val, "\\000") == 0)) {
    fprintf(vvp_out, "    %%pushi/str \"\";\n");
    return;
  }

  fprintf(vvp_out, "    %%pushi/str \"%s\";\n", val);
}

static void string_ex_substr(ivl_expr_t expr) {
  ivl_expr_t arg;
  unsigned arg1;
  unsigned arg2;
  assert(ivl_expr_parms(expr) == 3);

  arg = ivl_expr_parm(expr, 0);
  draw_eval_string(arg);

  /* Evaluate the arguments... */
  arg = ivl_expr_parm(expr, 1);
  arg1 = allocate_word();
  draw_eval_expr_into_integer(arg, arg1);

  arg = ivl_expr_parm(expr, 2);
  arg2 = allocate_word();
  draw_eval_expr_into_integer(arg, arg2);

  fprintf(vvp_out, "    %%substr %u, %u;\n", arg1, arg2);
  clr_word(arg1);
  clr_word(arg2);
}

static void string_ex_pop(ivl_expr_t expr) {
  const char* fb;
  ivl_expr_t arg;

  if (strcmp(ivl_expr_name(expr), "$ivl_darray_method$pop_back") == 0)
    fb = "b";
  else
    fb = "f";

  arg = ivl_expr_parm(expr, 0);
  assert(ivl_expr_type(arg) == IVL_EX_SIGNAL);

  fprintf(vvp_out, "    %%qpop/%s/str v%p_0;\n", fb, ivl_expr_signal(arg));
}

static void draw_sfunc_string(ivl_expr_t expr) {
  assert(ivl_expr_value(expr) == IVL_VT_STRING);
  draw_vpi_sfunc_call(expr);
}

void draw_eval_string(ivl_expr_t expr) {
  switch (ivl_expr_type(expr)) {
    case IVL_EX_STRING:
      string_ex_string(expr);
      break;

    case IVL_EX_SIGNAL:
      string_ex_signal(expr);
      break;

    case IVL_EX_CONCAT:
      string_ex_concat(expr);
      break;

    case IVL_EX_PROPERTY:
      string_ex_property(expr);
      break;

    case IVL_EX_SELECT:
      string_ex_select(expr);
      break;

    case IVL_EX_SFUNC:
      if (strcmp(ivl_expr_name(expr), "$ivl_string_method$substr") == 0)
        string_ex_substr(expr);
      else if (strcmp(ivl_expr_name(expr), "$ivl_darray_method$pop_back") == 0)
        string_ex_pop(expr);
      else if (strcmp(ivl_expr_name(expr), "$ivl_darray_method$pop_front") == 0)
        string_ex_pop(expr);
      else
        draw_sfunc_string(expr);
      break;

    case IVL_EX_UFUNC:
      draw_ufunc_string(expr);
      break;

    default:
      fallback_eval(expr);
      break;
  }
}
